(a) Technical Field
The present invention relates to a resonant converter. More particularly, the present invention relates to a resonant converter that enables high efficient precision control even at no load or light load in which low power is used.
(b) Background Art
Generally, DC/DC converters have been widely used in various industrial fields to convert an input DC voltage into an output DC voltage at a different level. The DC/DC converter converts a DC voltage into an AC voltage, and then the AC voltage is either raised or dropped by a transformer to be rectified again into a DC voltage, allowing the voltage to be transformed.
There are many circuit configurations for implementing the DC/DC converter, and one example thereof is a resonant converter. The resonant converter uses a resonant phenomenon of an inductor Lr and a capacitor Cr.
FIG. 11 is a view illustrating control characteristics of a resonant converter according to the switching frequency, which shows the resonant converter operating in a continuous conduction region has to increase the switching frequency to lower the output voltage. As an example, the switching frequency needs to further increase to lower a current from an output of 4 A to an output of 2 A.
However, when the switching frequency becomes higher, a switching loss of the resonant converter increases.
FIG. 12 is a view illustrating a loss of an Insulated Gate Bipolar Transistor (IGBT) when the output power (voltage and current) is lowered for the use at a light load region.
That is, in the DC/DC resonant converter operation in the continuous conduction region, the IGBT loss rapidly increases during the light load operation, and thus, the efficiency can be rapidly reduced or the switching element such as the IGBT can be damaged by burning.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.